I have lots of regular grade Neocaridina shrimplets from a well established planted tank available. They eat algae and fish food and need a tank that isn’t new with a sponge or mesh over the filter intake so they don’t get sucked up. Any fish with a mouth bigger than they are will eat them. They will live a couple years and produce babies to replace themselves if they have enough place for the hatchlings to hide. These are about 1.5 cm and they will grow up to 4 cm (males are smaller and less colourful than females).